Concrete masonry units (CMU) are typically produced in commercial block machines. The standard sized CMU or concrete block produced is 8 inches tall by 8 inches wide by 16 inches long and includes two large cores. This block is referred to as the 8-inch block and is the standard of the industry.
A block machine typically makes three 8″ blocks at a time, and those blocks are typically compressed and formed in about 10 seconds on the machine. The blocks are free standing after the forming step, and are then transported to a kiln in which low-pressure steam heat is applied to cure the concrete.
Another product that is commonly produced by the masonry industry is the concrete masonry veneer unit. As the veneer units are used to provide a facade on a building, they do not require the structural strength of an 8″ block and are typically produced with a 4-inch width. Although the standard veneer unit is typically 8″ tall by 16″ long, larger sizes are also desirable, including 12″ tall by 16″ long or even 16″ tall by 24″ long. To reduce the cost of the veneer units, block makers have added interior cores to the veneer block. The conventional veneer block produced on a commercial block machine is a nominal size of 8″ tall by 16″ long by 4″ wide.
During a ten second block making cycle, the mold goes into place in the machine, a feed drawer moves overhead with the concrete mix, the mix goes into the mold and slightly overfills it while at the same time the mold is vibrated mechanically to cause the mix to flow rapidly to the bottom of the mold, and an overhead compressive ram moves down and compresses the mix in the mold into its final shape. A standard 8″ block has a face shell thickness of about 1 inch. For the pour cycle of the block machine, the 1″ opening for the face shell becomes a limitation on production, as it is difficult to get the mix to drop down and fill the mold in the allotted cycle time. This becomes even more difficult when producing a standard veneer block, which has a face shell thickness of about ¾″. It is difficult to get the mix to flow into the narrow face shell area in the short time frame of the block making cycle. It is therefore very difficult to produce conventional hollow core veneer blocks on a commercial block machine, as a result of the difficulty in getting the mix to flow into the narrow mold in the short duration of the block making cycle.
There is now an increased demand for veneer blocks taller than the standard 8″ size. The added height of the taller hollow core veneer blocks makes it even more difficult to produce them in a commercial block machine. Tall veneer blocks, such as those 12″ tall by 16″ long or 16″ tall by 24″ long, are therefore produced as solid rectangular shaped blocks, which, since they lack cores and therefore lack the narrow face shell cavities in the mold, are easily filled by a commercial block machine. Although solid rectangular shaped veneer blocks are adequate for veneering the face of a building, they are not optimal as the solid block adds to both its weight and production cost.
What is needed therefore is a block that can be produced on a commercial block machine within a standard production cycle but with the weight and cost advantages of a conventional hollow core block.
The object of the present invention is to provide a veneer block having the weight and production cost advantages of a hollow core block but without a narrow face shell that limits production in a standard block machine.
These, and other objects and advantages will be apparent to a person skilled in the art by reading the attached description along with reference to the attached drawings.